hello, i had constructed ACDC convertor to measure wall voltage. Though i am a bit unsure whether it's safe to plug into Arduino. Our mains voltage is 230V, the transformer i'll be using has 9V secondary voltage and 1.9VA, as a diode bridge, i have KBPC1006 with 10A and 600V as a limit. Everything else is on the diagram (i think).
So my question is, whether this is safe to connect to Arduino analog input and ground? And whether it's safe to connect Arduino to computer via USB, because i need to watch serial monitor.
Safety depends on the transformer in this case, not much else.
The zener will make your readings non linear- so that can go...
The 6u8 will makes the readings ‘slow’. maybe try a 0.1u ceramic as a noise reducer.
I’d use 20k/10k for the divider - that will give you a 5v input for approx 15v at the (+) pin - should be fine for a AC 9v secondary... remember the output of the bridge rectifier will be the secondary (V x 1.4 = 12v7)
hey, thanks alot for response. Well, to be absolutely exact, my transformer looks like this. What did you mean by "slow"? By safety, i meant safety for arduino as well, i was worried about overflowing 5V input limit for Arduino and making some kind of short circuit problem by having it actively connected to computer via USB as well. The first thing as you said, depends on output of the bridge and choosing the right combination, so i guess 20k/20k would be okay, but 20/k/10k is better?
Thanks for help 
Slow, because the electro cap takes a finite time to charge & discharge..
Can be calculated accurately, but in this case - near enough is good enough!
20k/20k will divide the source voltage by two... 20==20, with the Vsense taken from the middle.
20k/10k will divide by 3 (15/3=5)... the total of the resistors will determine what current is wasted through the divider. (15/30000=0.5mA... you can work that out with ohms law)
Don't forget the error in the output voltage that is introduced by the non-linearity of the diode bridge. Low voltages will be affected the most.
lastchancename:
Slow, because the electro cap takes a finite time to charge & discharge..
Can be calculated accurately, but in this case - near enough is good enough!20k/20k will divide the source voltage by two... 20==20, with the Vsense taken from the middle.
20k/10k will divide by 3 (15/3=5)... the total of the resistors will determine what current is wasted through the divider. (15/30000=0.5mA... you can work that out with ohms law)
Oh right, i get it now. Well then you're right, i'll use 20k/10k, 10 as the bottom one and 20 as the top one. Thanks alot
aarg:
Don't forget the error in the output voltage that is introduced by the non-linearity of the diode bridge. Low voltages will be affected the most.
Yeah i realise this, this is basically fixed by the capacitor, isn't it?
No, sorry.
You're talking about the capacitor?
If you want to measure AC house voltage, a diode bridge is the wrong approach because of the voltage drop and extreme nonlinearity.
The OpenEnergyMonitor approach is safe and accurate.
jremington:
If you want to measure AC house voltage, a diode bridge is the wrong approach because of the voltage drop and extreme nonlinearity.The OpenEnergyMonitor approach is safe and accurate.
i wanted to get the rms value of the voltage, but this is a good idea as well, i was looking a bit for this. Someone told me about this website before but i couldn't find this. So thanks alot 
@jremington... that’s a great diagram... kudos.
Explains the levels really well.
This topic was automatically closed 120 days after the last reply. New replies are no longer allowed.